This invention generally relates to interlock systems for semiconductor fabrication systems, and is more particularly concerned with interlock systems which prevent transmission of gases to a processing chamber.
Fabrication of semiconductors typically involves performing a number of processes with respect to a substrate, such as a wafer. One commonly employed process is chemical vapor deposition (CVD). In CVD processing a wafer is placed in a processing chamber referred to as a deposition chamber. A process gas is flowed to the deposition chamber and interacts with the wafer to deposit a thin film on the wafer. The thin film deposited on the wafer may be, for example, a metal. During deposition processing it may also be desirable to flow a purge gas to a rear side of a pedestal on which the wafer is supported, to prevent thin film deposition on the rear side of the pedestal.
In a conventional deposition chamber, the chamber may include a lid that is removable to permit access to the interior of the chamber for maintenance or other purposes. It is also known to provide an additional lid that may be substituted for the regular lid. The additional lid may have transparent panels or viewports formed therein to allow viewing of the interior of the chamber during maintenance operations such as calibration of a wafer-handling robot that inserts wafers into the chamber and removes wafers from the chamber.
Many process gases used for CVD are toxic. Accordingly, it is known as a safety measure to provide an interlock arrangement that prevents gases from flowing to the deposition chamber when no lid is present on the chamber. As is familiar to those who are skilled in the art, the interlock arrangement overrides any instructions from the system controller by closing a valve or valves so that gas flow to the deposition chamber is cut off.
The present inventors have recognized that it would be desirable to provide additional safety measures at times when maintenance functions are being performed with respect to deposition chambers.
One aspect of the invention provides a method of operating a processing chamber, where the processing chamber has associated with it a mechanism for selectively transmitting a plurality of gases to the processing chamber, and the plurality of gases includes at least one toxic gas. The method according to this aspect of the invention includes actuating a first interlock condition to prevent transmission of all of the plurality of gases to the process chamber when no lid is situated in a closed position on the processing chamber. The method further includes actuating a second interlock condition to prevent transmission of the at least one toxic gas to the processing chamber when a first lid (a lid installed for a maintenance operation) is situated in a closed position on the processing chamber. Also included in the method is the step of allowing all of the plurality of gases to be transmitted to the processing chamber when a second lid (installed for normal processing such as CVD processing) is situated in a closed position on the processing chamber.
The multiple levels of interlocks provided in accordance with the invention, with all gas flow being prevented or xe2x80x9cinterlockedxe2x80x9d when no lid is present, and toxic gas flow being interlocked when the lid for maintenance is present, provides for enhanced safety during maintenance operations.
The multiple levels of interlocks may be implemented by providing two separate switches on the processing chamber. The lid employed for normal processing operations (the xe2x80x9cprocessing lidxe2x80x9d) may be equipped with a pair of tabs adapted to respectively actuate the two switches. The lid used for maintenance operations may be equipped with only one tab, which actuates only one of the switches when the maintenance lid is in place on the processing chamber. Accordingly, when neither switch is actuated, the first interlock condition is actuated, so that all gases are prevented from flowing to the processing chamber. When one of the switches is actuated but the other is not (e.g., due to presence of the maintenance lid), then the second interlock condition is actuated, such that transmission of toxic gases to the processing chamber is prevented but transmission of non-toxic gases is still enabled. When both switches are actuated (e.g., by the processing lid), no interlock is in effect, so that all gases are allowed to flow to the processing chamber.
Other objects, features and advantages of the invention will become more fully apparent from the following detailed description of the exemplary embodiments, the appended claims and the accompanying drawings.